The present invention relates to a random number data generator capable of outputting data at random timings.
There has been contrived heretofore a random number data generator which outputs data at random timings (random number data) by employing an oscillator. Here, the random number data generator is a circuit to generate random number data by utilizing variations of the output timings, wherein the security of the whole system can be enhanced by the use of such random number data.
In order to secure sufficiently the variations of the output timings, the cycle of outputting the random number data is set to be much longer than the oscillation cycle of the oscillator.
In case the random number data are used in a logic circuit, the random number data generator latches the output signal of the oscillator in synchronism with a system clock signal of the logic circuit and then outputs the latched signal as random number data.
However, since the oscillation cycle of the oscillator is unstable to any change of a supply voltage or the like, it has been customary that the cycle of the latching action needs to be longer than an actually required cycle so as to secure sufficiently the variations of the output timings by ensuring that the number of oscillations are greater than a certain value as mentioned within one cycle of the latching action.
In the related art, a plurality of such oscillators is provided in parallel to increase the amount of the random number data. However, if any one of the oscillators is brought to a halt due to some factor, there may arise a problem that the level of the random number data generated from the corresponding oscillator is fixed to fail consequently in completely ensuring the security of the whole system including the oscillators.